How many watts do I need?

A gaming PC with a GeForce RTX 5070 Ti or Radeon RX 9070 XT needs a 750 W power supply by NVIDIA's and AMD's own figures, and 850 W is the size to buy. The rule for any card is one size above the maker's figure: 650 W for an RTX 5060, 750 W for an RTX 5070, 1,000 W for an RTX 5080 and 1,200 W for an RTX 5090.

The step up costs little. On Amazon UK at the time of writing (October 2026), the cheapest 850 W ATX 3.1 unit in Compare Electronic's price table, the Corsair RM850e (2025), costs £89.99, the same as the cheapest 750 W unit. The cards themselves are ranked in Best graphics card UK 2026.

What PSU does each RTX 50 and RX 9000 card need?

NVIDIA and AMD ask for 450 W to 1,000 W across the two ranges, from the Radeon RX 9060 XT at 450 W to the GeForce RTX 5090 at 1,000 W. NVIDIA bases its figures on a PC with a 16-core Ryzen 9 9950X, so they already allow for a high-end processor; AMD calls its figure a minimum recommendation.

Board partners can ask for more than NVIDIA or AMD. ASUS lists 850 W for the ASUS TUF Gaming GeForce RTX 5070 Ti and the ASUS ROG Strix GeForce RTX 5070 Ti OC, 100 W above NVIDIA, but 750 W for the ASUS Prime GeForce RTX 5070 Ti OC. Sapphire lists 850 W for the NITRO+ RX 9070 XT, which it rates at 330 W against AMD's 304 W. The figure on the card maker's own page is the one to meet. Whether the card needs a 16-pin cable is covered in Do I need a 12V-2x6 cable?

How much headroom does a gaming PC need?

Enough to keep the estimated full load at or below 80% of the power supply's rating. Compare Electronic adds the graphics card's rated power, the processor's rated power and 100 W for the motherboard, memory, drives and fans. At the makers' figures, three of these nine builds pass 80%; at Compare Electronic's sizes, none passes 76%.

Processor figures are AMD's rated TDP (65 W for the Ryzen 5 9600X, 120 W for the Ryzen 7 9800X3D, 170 W for the Ryzen 9 9950X) and Intel's 250 W maximum turbo power for the Core Ultra 7 270K Plus, the chip that pushes an RTX 5070 Ti build to 87% of 750 W. The processors are compared in Best CPU for gaming UK 2026. The 80% line is Compare Electronic's rule, not a standard. It keeps the unit away from full load, where be quiet! rates the Pure Power 13 M 1000W at 92.5% efficiency and 19.5 dB(A), against 94.4% and 8.6 dB(A) at half load.

Power spikes:an ATX 3.1 power supply has spike tolerance built in. Gigabyte says the AORUS ELITE P850W, compliant with Intel's ATX 3.1 standard, sustains excursions of up to twice its total rating and three times the graphics card's power. MSI rates the MAG A850GLS PCIE5 at 1,870 W for 100 microseconds, 220% of its 850 W rating, and NVIDIA recommends a PCIe CEM 5.1 compliant power supply for every RTX 50 card. An older unit without an ATX 3.x rating publishes no such figure, which is the case for sizing it up or replacing it.

Is 850 W or 1,000 W worth the extra money?

Yes, because the step costs little or nothing. Across three ATX 3.1 ranges on Amazon UK at the time of writing (October 2026), 850 W costs between £9.01 less and £30.82 more than 750 W, and 1,000 W costs between £12.57 less and £4.91 more than 850 W.

List prices no longer track wattage. The Corsair RM850e (2025) costs £9.01 less than the RM750e (2025), and the be quiet! Pure Power 13 M 1000W costs £12.57 less than its 850 W sibling. Per watt, the Corsair RM1000e (2025) is the cheapest unit in the table at 9.5p, against 10.0p for the be quiet! Pure Power 13 M 1000W, 10.6p for the Corsair RM850e (2025) and 12.0p for the be quiet! Pure Power 13 M 750W. The MSI MAG A1000GLS PCIE5 costs 96p more than the MSI MAG A850GLS PCIE5.

Which power supply should you buy?

The Gigabyte AORUS ELITE P850W is the pick for an RTX 5070 Ti or RX 9070 XT build, at £107.09 on Amazon UK at the time of writing (October 2026). Gigabyte rates it at 850 W with 80 Plus and Cybenetics Platinum efficiency, a native 600 W 16-pin cable and a 10-year warranty, in a 140 mm body.

Platinum efficiency separates it from the Gold units here: Gigabyte quotes 92% at typical load. With six PCIe 6+2 connectors as well as the 16-pin cable, it powers 8-pin Radeon cards without an adapter. The fan stops below 50% load, or 425 W, so it stays silent through desktop work. Buyers who want the lowest price at 850 W should take the Corsair RM850e (2025) at £89.99, £17.10 less, with a 7-year warranty.

Verdict

Buy one size above the wattage NVIDIA or AMD lists for the card, and meet the card maker's own figure where it is higher. For an RTX 5070 Ti or RX 9070 XT that means 850 W: the Gigabyte AORUS ELITE P850W at £107.09 is the pick and the Corsair RM850e (2025) at £89.99 the cheapest, on Amazon UK at the time of writing (October 2026). An RTX 5080 build should take the be quiet! Pure Power 13 M 1000W at £99.99. The cards are ranked in Best graphics card UK 2026, and ready-built PCs that arrive with a matched power supply in Best gaming PC UK 2026.